Video | Business Headlines | Internet | Science | Scientific Ethics | Technology | Search


NIWA survey work helps assess Kaikoura tsunami risks

22 March 2013

NIWA survey work helps assess Kaikoura tsunami risks

Surveying work carried out by NIWA scientists this week is helping provide new insights into the tsunami risk from undersea landslides in the Kaikoura Canyon.

The Kaikoura Canyon is a submarine canyon just off the east coast of the South Island, and connects the continental shelf with deep ocean basins to the north. Submarine landslides are one of the main processes that create submarine canyons. Landslides in the head of Kaikoura Canyon are thought to occur about once every 200 years on average.

Modelling by NIWA scientists in 2006 looked at the potential severity of tsunamis off the Kaikoura coast, either triggered by submarine earthquakes or as a result of a submarine landslide of sediment occurring at the head of the Kaikoura canyon.

The modelling showed that a submarine landslide at the head of the canyon would cause a significant tsunami that would arrive in South Bay with very little warning, with the crest of the wave about 13 metres above sea level (see below for more details).

Now NIWA scientists are using new technology to determine the size, shape and physical character of the sediment deposit in order to further assess the tsunami hazard if a landslide occurred.

“This is the most dynamic and active submarine canyon on the New Zealand margin, coming to within 500 metres of the shoreline and dropping to 1000 metres deep within 5 kilometres of the shoreline,” says NIWA Marine Geologist Dr Joshu Mountjoy.

“Kaikoura is a very active seismic region and with the potential for large earthquakes, any unstable sediment could collapse during a good shake and generate a tsunami. We need to know just what the hazard is from such events to ensure the resilience of coastal communities.”

By collecting multibeam bathymetric data, boomer seismic reflection data and sediment core samples, the team mapped the shape of the seafloor, determined the thickness of the sediment and collected sediment samples to analyse how much sediment is accumulating in the canyon head due to ocean currents and large storm activity.

“Since the previous work was carried out on the Kaikoura Canyon head in the 1990s, new scientific techniques now allow us to determine the rate at which sediment has accumulated here over the last century” says NIWA scientist Dr Alan Orpin “and this has big implications for how much sediment accumulates in the canyon head” he adds.

Geophysical data collected this week will be combined with a geotechnical field and laboratory investigation of the sediment deposit and then fed into new tsunami source and inundation modelling to get a better idea of the scale of the potential tsunami risk.

“The best result from this work would be that the amount of sediment at the head of the canyon has been over-estimated in the past and the hazard is much lower that thought – but we won’t know the answer to that until we have analysed the new data collected this week,” says Dr Mountjoy.

NIWA’s survey vessel Ikatere was used to do the survey work, which is co-funded by NIWA and Environment Canterbury.

More information:

What did the 2006 modelling show if there was a submarine landslide from head of Kaikoura canyon?

The moment the landslide happens would be dramatic for anyone in a boat off the coast. Water around the canyon head walls would appear to be sucked down creating a large hole with a pinnacle of water rising in the centre. Large waves radiate out, some following of the direction of the sliding mass of sediment below. However, the biggest waves radiate back towards Goose Bay and Oaro.

All this happens very quickly. The tsunami’s first wave arrives at Goose Bay just one minute after the landslide starts. The wave crest is about 13 metres above sea level. A smaller wave, slightly less than 2 metres high, reaches Kaikoura about 15 minutes after the landslide, and a sequence of waves arrive at the township for almost an hour.

How likely are such tsunamis?

Kaikoura is in a highly seismically active region, but not all earthquakes are of sufficient magnitude to trigger tsunamis.

The recurrence intervals on the submarine faults in this study are long – in the order of tens of thousands of years. In general, the recurrence intervals for other faults in the area are much shorter. Submarine landslides in the canyon, however, are thought to occur about once every 200 years on average.

For more information about NIWA’s research vessel Ikatere – click here.


© Scoop Media

Business Headlines | Sci-Tech Headlines


DIY: Kiwi Ingenuity And Masking Tape Saves Chick

Kiwi ingenuity and masking tape has saved a Kiwi chick after its egg was badly damaged endangering the chick's life. The egg was delivered to Kiwi Encounter at Rainbow Springs in Rotorua 14 days ago by a DOC worker with a large hole in its shell and against all odds has just successfully hatched. More>>


Trade: Key To Lead Mission To India; ASEAN FTA Review Announced

Prime Minister John Key will lead a trade delegation to India next week, saying the pursuit of a free trade agreement with the protectionist giant is "the primary reason we're going" but playing down the likelihood of early progress. More>>



MYOB: Digital Signatures Go Live

From today, Inland Revenue will begin accepting “digital signatures”, saving businesses and their accountants a huge amount of administration time and further reducing the need for pen and paper in the workplace. More>>

Oil Searches: Norway's Statoil Quits Reinga Basin

Statoil, the Norwegian state-owned oil company, has given up oil and gas exploration in Northland's Reinga Basin, saying the probably of a find was 'too low'. More>>


Modern Living: Auckland Development Blowouts Reminiscent Of Run Up To GFC

The collapse of property developments in Auckland is "almost groundhog day" to the run-up of the global financial crisis in 2007/2008 as banks refuse to fund projects due to blowouts in construction and labour costs, says John Kensington, the author of KPMG's Financial Institutions Performance Survey. More>>


Health: New Zealand's First ‘No Sugary Drinks’ Logo Unveiled

New Zealand’s first “no sugary drinks logo” has been unveiled at an event in Wellington... It will empower communities around New Zealand to lift their health and wellbeing and send a clear message about the damage caused by too much sugar in our diets. More>>


Get More From Scoop

Search Scoop  
Powered by Vodafone
NZ independent news